Maybe Nerlens Noel would have blown out his knee, no matter where he was playing.

But if Noel — Everett native, University of Kentucky freshman, and presumptive number one NBA draft pick — had shredded his left anterior cruciate ligament last month during a professional game, rather than a college contest, his fortunes would be very different.

The 6-foot, 10-inch, shot-blocking savant is good enough to be making millions in the NBA right now. But the league’s minimum age requirement of 19, which is lucrative for both the NBA and the National Collegiate Athletic Association, delayed Noel’s payday.

When he crumpled to the floor against conference rival Florida, casting doubt over his promising future, Noel rekindled a national debate about the merit, fairness, and even the legality of the NBA’s eligibility rule.

“It’s blatant age discrimination,” said Louis Pechman, a New York labor lawyer who has studied the NBA’s age rule and believes it is illegal. “If I’m 18 and this is my meal ticket, it’s ridiculous. I can work at General Motors; I can work at McDonald’s. Why can’t I work in the NBA?”

Had Noel been eligible for the 2012 NBA draft, he might have been selected as high as third overall. Last year’s actual number three pick, Bradley Beal, is making $4.1 million in the first season of a four-year, $18.7 million contract with the Washington Wizards. He earns even more from an endorsement deal with Nike.

Instead of a contract and endorsement, Noel got a scholarship worth about $30,000. Though he owns an insurance policy that would pay him in the case of a career-ending injury, Noel still faces eight months of rehabilitation before he can begin the pro career for which he was qualified last year.

The rule’s benefits to the NBA are clear. For one thing, the public exposure players receive in college makes them more valuable marketing assets as rookies than they would be if they entered the league directly from high school, said Stephen McKelvey, director of the sport management graduate program at the University of Massachusetts Amherst.

Only hard-core basketball fans were familiar with Anthony Davis, last year’s number one draft pick, when he was a senior at the Perspectives Charter School in Chicago. But even casual fans knew him after he led Kentucky to a national championship as a freshman.

Noel, known for his box-top afro that recalls Will Smith’s hairdo in “The Fresh Prince of Bel Air,” appeared to be on his way to similar fame.

“It’s very helpful from a marketing standpoint to have players make a March Madness run, like an Anthony Davis or a Carmelo Anthony,” said a former NBA executive who declined to be identified because he’s no longer authorized to speak for the league. “That’s very real.”

The NCAA, also, has an obvious incentive to back an NBA age restriction. Having top prospects play at least one season of college basketball makes fans more likely to watch amateur games on television, said Roger Noll, an economics professor at Stanford University who has studied sports broadcast deals.

A budding star can elevate a regular-season game involving a mediocre team into appointment television, Noll said.

Rights to broadcast the NCAA’s postseason men’s basketball tournament have become far more expensive since the NBA age requirement was implemented, though many factors contributed to the hike. In 2010, CBS and Turner Sports agreed to pay the NCAA $10.8 billion over 14 years for the right to broadcast its annual tourney — a 41 percent rate increase from a deal signed in 2002, when standouts were free to turn pro after high school.

The payoff for players compelled to put their professional aspirations on hold is less apparent. While Noel’s insurance policy would reportedly pay him $10 million in the event of a career-ending injury, the age rule has forced the son of Haitian immigrants to wait a year before offering financial assistance to his family.

Noel spent two years at Everett High before he transferred to the private Tilton School in New Hampshire. He told ESPN in 2011 that his mother, Dorcina, was separated from his father and worked two jobs to support him and three siblings until back injury made such rigor impossible. He said his mother’s struggle has driven him “to make it for myself and my family.”

Kentucky declined to make Noel available for an interview, and neither of his parents responded to interview requests.

The former NBA executive argued that for many players, the maturity they gain in college makes them better — and, eventually, higher-paid — professionals. But in the short term, he acknowledged, the rule “is a tremendous economic disadvantage for the players.”

“Every year spent in college is one less year making big money,” he said.

The age restriction was the headline provision of a collective bargaining agreement the NBA and its players union reached in 2005, and it went into effect with the following year’s draft. Before then, prodigies like Kevin Garnett, Kobe Bryant, and LeBron James transitioned successfully from preps to pros and became superstars.

But some others quickly washed out of the league, costing the franchises that drafted them millions of wasted dollars.

When Representative Steve Cohen of Tennessee pressured the NBA to lift its age requirement in 2009, threatening to hold congressional hearings on the matter, league president Joel Litvin wrote in a letter to Cohen that the rule is a product of “business considerations.”

Mandating that draft entries be at least 19 years of age, Litvin said, is about “increasing the chances that incoming players will have the requisite ability, experience, maturity, and life skills.”

A Globe analysis of player statistics, draft positions, and scouting reports suggests that the rule has helped NBA franchises make smarter business decisions. The Globe compared the 51 college freshman who have been drafted in the seven years since the age restriction was implemented to the 29 high school seniors who were drafted in the seven years prior. The review showed that players have performed better as professionals after a year in college and that their draft positions have often differed significantly from their rankings in high school.

The players who spent one season in college have averaged more points, rebounds, and assists per game in the NBA than the players who were drafted out of high school did at the same stages of their careers. The college freshmen were drafted an average of 3.2 positions higher than the high school seniors.

Within each draft class of “one-and-done” college players, the Globe compared the players’ actual NBA draft order to their average ranking as high school seniors by four major scouting organizations — ESPN, Rivals.com, MaxPreps, and Scout.com. For example, the actual draft order of college freshmen in 2009 was Tyreke Evans, DeMar DeRozan, Jrue Holiday, Byron Mullens. When the same players were high school seniors, Mullens was rated first, Holiday second, Evans third, and DeRozan fourth.

In an average draft class with 7.3 college freshman, a typical player’s position changed by 1.8 spots after a year of college basketball.

The 25 percent shift in class rank suggests that despite advances, evaluating high school talent remains an inexact science. Andre Drummond, the fourth freshman taken in last year’s NBA draft and the ninth pick overall, was rated the number twoprospect in the country as a high school senior by ESPN and Scout.com but was not among MaxPrep’s top 100 or Rivals.com’s top 150.

Recognizing the value of additional scouting time, NBA Commissioner David Stern has said that he would like to raise the age minimum to 20, which would nudge the league closer to the waiting period it enforced in the 1960s: four years after high school.

When that rule was challenged in 1971 by Spencer Haywood, an American Basketball Association star who signed with the NBA’s Seattle SuperSonics only three years out of high school, the Supreme Court ruled, 7-2, that the league’s ban on young players constituted an illegal group boycott.

Affirming a lower court’s ruling, the Supreme Court held that “if Haywood is unable to continue to play professional basketball for Seattle, he will suffer irreparable injury in that a substantial part of his playing career will have been dissipated . . . and a great injustice will be perpetrated on him.”

The decision effectively ended the NBA’s practice of keeping players out of the league on the basis of age, until it applied the current restriction in 2006.

Pechman, the labor lawyer, said he would love to mount a legal battle similar to Haywood’s, though he would allege age discrimination, not a violation of antitrust law.

“Bring the case in New York,” where the NBA is headquartered, Pechman said. “I’ll file it tomorrow.”

But Noel appears unlikely to become the star plaintiff. He has given no indication that he would fight the league in court, and his focus now is on his recovery, according to Ken Hollingsworth, the Tilton School’s athletic director.

“I’ve texted with him a bit, and he’s maintaining a good attitude,” Hollingsworth said. “I know he’s going to work hard, and I believe he’ll overcome this.”

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